For towed vehicles, such as trailers, it is common to provide a self-contained hydraulic braking system that operates independently of the braking system on the towing vehicle. A surge brake actuator allows the towed vehicle to utilize its own braking system that operates when the towing vehicle brakes. The surge brake actuator generally includes a coupler housing component attached to the towing vehicle and a hydraulic cylinder component that actuates the brakes on the towed vehicle. The surge brake actuator operates in such a manner that when the towing vehicle brakes, the towed vehicle's forward momentum creates a decelerating force on the towing vehicle and the coupler housing attached to the towing vehicle. The hydraulic cylinder utilizes the resultant decelerating force on the coupler housing component to create a fluid pressure that actuates the brakes of the towed vehicle.
The output pressure of the braking system is a function of the ability of the brake actuator to convert the deceleration forces provided by the towing vehicle into hydraulic pressure to actuate the towed vehicle brakes. This force/pressure ratio is an important component in the ability of an actuator to provide braking pressure to the towed vehicle. To date, various designs of known brake actuators inefficiently convert the decelerating force to fluid pressure. Reasons for such inefficient conversion of the decelerating force to fluid pressure include: a build-up of road debris in the actuator; corrosion or rust bonding of actuator components; high frictional loss from actuator components; and coupler housing interference.
Breakaway mechanisms on brake actuators are generally known. These mechanisms generally operate through a cable or chain that is attached to a towing vehicle by means of an S-hook or similar attachment device. The opposite end of the cable is operably connected to the towed vehicle's braking system. When the towed vehicle becomes detached from the towing vehicle during operation, the towed vehicle, no longer being pulled by the towing vehicle, tends to change position relative to the towing vehicle. The S-hook, however, remains attached to the towing vehicle. As the towing vehicle pulls the cable, the cable actuates the towed vehicle brake mechanism, thereby stopping the towed vehicle. To maintain pressure on the cable and prevent the cable from releasing the towed vehicle braking mechanism, a friction lock is generally used to prevent the cable from retracting and prematurely releasing the towed vehicle brake. Although such mechanisms are generally adequate to stop a breakaway trailer in most circumstances, they do possess several inherent drawbacks.
Most known systems operate by means of a friction lock to prevent the extended cable from retracting. During connection and disconnnection of the towed vehicle to the towing vehicle, the cable is often pulled toward the towing vehicle. Even a slight tug is often enough to actuate the breakaway mechanism slightly, or to cause dangerous slack in the cable when the friction lock prevents the cable from returning taught after connection to the towing vehicle. Even though the brake mechanism may be actuated only somewhat, this slight activation can cause excessive wear on the towed vehicle brake and an excessive burden on the pulling vehicle that decreases fuel mileage and increases maintenance costs. Over time, this excessive burden could even cause the towed vehicle brake to fail in an emergency situation due to premature lining wear or overheating.
Another feature found on certain brake actuators is a reverse lock-out assembly. Known reverse lock-out assemblies prevent accidental actuation of the towed vehicle brakes when the towing vehicle backs up or reverses. These known reverse lock-out assemblies are not reliable because they allow for the possibility of accidentally disengaging while the towing vehicle moves in reverse. Additionally, the design of these reverse lock out assemblies are awkward to use, which can also increase the unreliability of such known assemblies.
It would be beneficial to have a surge brake actuator that can overcome these problems associated with the inefficient conversion of decelerating force to fluid pressure. Furthermore, it would be beneficial to provide improvements to one or more of the components of the surge brake actuator that would improve the force/pressure conversion.
It would also be beneficial to have a surge brake actuator having a breakaway mechanism that safely and reliably operates when the actuator decouples from the towing vehicle.
It would also be beneficial to have a surge brake actuator having a reverse lock-out assembly that is simple to use and reliably prevents brake actuation when the assembly is engaged and the towing vehicle operates in reverse while reliably disengaging when the towing vehicle moves forward.